Filtered-orthogonal frequency division multiplexing (F-OFDM) is sub-band filtering-based OFDM. In an F-OFDM waveform technology, a spectrum is divided into a plurality of sub-bands, and numerology of different sub-bands may be the same or may be different. Numerology of a sub-band includes at least one of the following parameters such as subcarrier bandwidth, a transmission time interval (TTI) length, a symbol length, a quantity of symbols, and a cyclic prefix (CP) length. The numerology of the sub-band may be preconfigured, or may be flexibly adapted based on service load. Different sub-bands may be used for different types of services. For example, a conventional voice/video, the Internet of Things (IOT), a real-time Internet of Vehicles, and a Multimedia Broadcast Multicast Service (MBMS) are respectively distributed in different sub-bands. Then, each sub-band is filtered, for example, a higher-order digital molding filter is used for filtering. The filtered sub-band has good out-of-band performance, so as to implement decoupling of each sub-band. Therefore, when a conventional OFDM waveform is compatible, different numerology may be configured for sub-bands based on an actual service scenario.
A higher order of a filter indicates a better out-of-band feature, but indicates higher implementation complexity. Therefore, a low-complexity filter design is a core problem in F-OFDM application. However, a multiple-input multiple-output (MIMO) technology is one of most basic technologies in a wireless communications system, and any new technology, including the F-OFDM, needs to be used in combination with the MIMO technology. When the F-OFDM is applied to a MIMO system, a time domain signal on each antenna port needs to be filtered in the prior art. Therefore, for a sub-band, a total quantity of filtering operations of a transmitter is equal to a product that is obtained by multiplying a quantity of filtering operations on one antenna port by a total quantity of transmit antennas, and filtering complexity is relatively high.